Above: The hideout of Al-Qaeda leader Osama bin Laden is pictured after his death by US Special Forces in a ground operation in Abbottabad on May 2, 2011. Pakistan said that the killing of Osama bin Laden in a US operation was a 'major setback' for terrorist organisations and a 'major victory' in the country's fight against militancy.

Speaking at the White House, Obama said bin Laden's death showed that the United States has kept its commitment to seeing that justice is done.

"We can all agree this is a good day for America," the president said during a Medal of Honor ceremony in the East Room. "The world is safer."

Bin Laden, the force behind the Sept. 11, 2001, terrorist attacks that killed thousands of people, was killed by a small team of U.S. Navy special forces during a 40-minute operation at a compound in the Pakistani town of Abbottabad, north of the capital, Islamabad.

SEAL Team 6 used four helicopters to swoop down on the three-story, fortress-like compound early Monday. A firefight erupted and bin Laden was shot in the head. Several other adults also were killed, including one of the al-Qaida leader's sons and a woman who reportedly was used as a human shield. One helicopter was lost in the operation due to a mechanical failure and destroyed by the crew, who flew out in the remaining three choppers along with bin Laden's remains.

A senior intelligence official told reporters at a Pentagon briefing Monday afternoon that Bin Laden's body was later transported to the aircraft carrier USS Carl Vinson in the north Arabian Sea. It was washed in accordance with Islamic practices and placed in a white sheet and then put in a "weighted bag," the official said.

A military officer read prepared "religious remarks" that were translated into Arabic by a "native speaker" who was not further identified. The body was then placed on a "prepared flat board, tipped up, whereupon the deceased's body eased into the sea," the official said.

White House officials were mulling the merits and appropriateness of releasing a photo, but senior administration officials said that DNA testing alone offered a near 100 percent certainty that bin Laden was among those shot dead. Photo analysis by the CIA, confirmation by a woman believed to be bin Laden's wife on site, and matching physical features like bin Laden's height all helped confirmed the identification.

In a memo to CIA employees on Monday, the agency's director, Leon Panetta, hailed the demise of "the most infamous terrorist of our time," but he warned that "terrorists almost certainly will attempt to avenge" the killing of their leader.

"Bin Laden is dead. Al-Qaida is not," Panetta said.

Secretary of State Hillary Clinton echoed those remarks, saying the threat from al-Qaida "will not end with the death of Osama bin Laden."

"The fight continues and we will never waver," she said, adding in a direct message to bin Laden's followers, "You cannot wait us out."

It was unclear how much — if any — involvement Pakistan had in the operation or even whether Islamabad was aware of the U.S. raid in Abbottabad until after the assault was over.

U.S. officials said Monday that Pakistan had been left in the dark about the operation and only informed after its successful completion. But Clinton said later that counterterrorism cooperation with Pakistan had helped lead the U.S. to the compound where bin Laden was hiding.

Speaking to reporters at the State Department on Monday, Clinton thanked Pakistan for its cooperation and said the country "has contributed greatly to our efforts to dismantle al-Qaida.'"

Abbottabad, about 40 miles north of Islamabad, is home to three army regiments and the Kakul Military Academy, an army officer training center. The location of bin Laden's compound raised pointed questions about what Pakistani officials knew about his whereabouts.

Sen. Joseph Lieberman, the chairman of the Senate Homeland Security Committee, said Pakistan must demonstrate that it had no knowledge of bin Laden's whereabouts.

"This is going to be a time of real pressure" on Pakistan "to basically prove to us that they didn't know that bin Laden was there," Lieberman (I-CT) said at a news conference.

"I think the Pakistani army and intelligence have a lot of questions to answer, given the location, the length of time and the apparent fact that this facility was apparently built for bin Laden," said Sen. Carl Levin (D-MI).

Steve Coll, author of Ghost Wars and The Bin Ladens, said it is not surprising that the terrorist leader was found in an urban area instead of in the mountainous region near the Afghan border where he was once thought to have been hiding.

"It seems as if he moved to this compound after 2005," in an effort to avoid aerial drones, Coll told NPR. It's likely that bin Laden "would seek refuge in someplace that he considered less susceptible to aerial surveillance and attack."

The compound where bin Laden was found "was a relatively isolated one that seems to have been purpose-built to hold him," Coll said, adding that the house "seems to have strange security features," and armed men living there along with bin Laden.

The president, in his remarks on Monday, praised the crowds of people who gathered spontaneously at the White House, in New York and across the nation after the news of bin Laden's death, saying the celebrations embodied the true spirit and patriotism of America.

On the streets of Washington, D.C., people like Edith Briggs said they shared a sense of relief, but also some nervousness over the possibility of retaliatory terrorist attacks.

"I am very happy, but I am also on guard because I think they are going to try something," she said in reference to al-Qaida.

Meanwhile, Muslim clerics questioned the U.S. decision to bury bin Laden at sea, saying it marked a violation of Islamic custom.

Obama said the remains had been handled in accordance with Islamic custom, which requires speedy burial. But a wide range of Islamic scholars interpreted it as a humiliating disregard for the standard Muslim practice of placing the body in a grave with the head pointed toward the holy city of Mecca.

They said sea burials are allowed only in special cases where the death occurred aboard a ship.

"The Americans want to humiliate Muslims through this burial, and I don't think this is in the interest of the U.S. administration," said Omar Bakri Mohammed, a radical cleric in Lebanon.

A U.S. official, who asked not to be named, said the burial decision was made after concluding that it would have been difficult to find a country willing to accept the remains. There was also speculation about worry that a grave site could have become a rallying point for militants.